Fatty acid mixtures and soaps derived therefrom



United States Patent LouA. Stegemeyer, Cincinnati, Ohio, assignor toEmery Industries, Inc., Cincinnati, Ohio, a corporation of ChicApplication October 30, 1953, Serial No. 389,487

4 Claims. (Cl. 252-108) No Drawing.

.This invention relates to compositions of fatty acids which may beemployed to enhance certain desirable physical properties of soaps.

.By the term soaps is generally meant the sodium and potassium salts ofaliphatic monocarboxylic acids having 12 to 18 carbon atoms in thechain. Soaps are produced in various physical forms such as inconcentrated solutions in water, the so-called liquid soaps, in the formof bars or in flakes or granules. Soaps are also produced for variousspecific purposes, for example, toilet soaps, general household soaps,textile soaps, etc.

-The variation in physical properties and in other properties forspecific uses are achieved by selection of the appropriate oil or fatorblends of oils or fats used to manufacture the soap and by selectionof the alkali used for saponification. Modifications in properties mayalso beza'chieved by selectioniand variation in the alkaline builderswhich are often incorporated in soaps but such modifications are not thesubject matter of this invention.

For soap-making purposes, the various oils and fats differ from oneanother primarily in the kind and proportions. of the various higherfatty acids which they contain. Thus, the fats which are liquid atnormal temperatures, generally termed fattyoils, contain higherpercentages of .the unsaturated normally liquidacids, such as oleic,linoleic, and linolenic acids. The lower melting animal ,fats,.such ashog fats or greases, contain moderate amounts of .the normally solidsaturated fatty acids, such as'stearic and palmitic acids, and thehigher melting animal fats, such as beef fat or tallow, contain stillgreater percentages of the solid acids. V

.rCertain of the tropical vegetable oils such as palm kernel oil'andcoconut oil are characterized by a high content of saturated acids ofshorter chain length than stean'c and palmitic, namely lauric andmyristic acids.

gAs a'very rough generalization, the unsaturated liquid acids. producesoaps which are physically soft and readily soluble in water. The solidacids of C16 and Cmcarbon chain length produce hard soaps which arereadily soluble only in hot water. The saturated acids oflower chainlength produce hard soaps which, however, are quite soluble in water atnormal temperatures. The terms hard and soft, as used, refer to thephysical characteristics of the soaps with a normal moisture content of20 30% as even the soaps of the unsaturated acids can be produced in asolid form when dried to a sufiiciently low moisture content. Allpercentages and proportions disclosed herein are by weight.

. The alkali most'commonly used to neutralize the acids is sodiumhydroxide, but potassium hydroxide, which is more costly, may be usedwhere the maximum of water solubility is desired. Potassium hydroxide isalso used extensively in the manufacture of concentrated liquid soapswherein clarity at low temperature is desired.

theselection and blending of fats and oils to obtain appropriate fattyacid compositions, or by the addition ofspecific previously separatedfatty acids, and by the choice of alkalia wide variety of physicalcharacteristics 2 and solubilities can .be obtained. One of the morediflicult combinations of properties to achieve satisfactorily is thatof a high degree of solubility and appropriate physical firmness. One ofthe most useful fats to enhance these properties is coconut oil orcoconut fatty acids. Coconut oil may be used either alone or blendedwith other'fats for a variety of purposes. Liquid soaps of 35 to 36%soap content, in .which the high water solubility of the soap isutilized, usually contain a high per centage of coconut oil. Coconut oilis also used in toilet soaps as it increases the firmness of the cakewhile at the same time increasing the ease of solubility andthe amountof lather produced. Coconut oil may also be used in granulated soaps toprevent the granules from gumming and sticking together when introducedinto water.

.Although coconut oil is a very versatile raw material for the soapmaker and, therefore, is widely used, there are certain'disadvantagesattendant to its use. Its price is subject to wide variations which areoften independent of the prices of other fats. Being produced far fromthe point of use, the supply of coconut oil is often erratic. The soapsof coconut oil are also considered to be irritating to the skin,affecting some individuals more than others. This undesirable propertytends to limit its use. Attempts have been made to reduce the irritatingprop erty by removing the lower molecular weight C6 to C10 acids, whichare present to the extent of about 15%, usually by fractionaldistillation of the acids. There appears, however, to be considerabledifference of opinion as to whether this treatment is eifective orwhether the irritation is due to some other cause.

It is the purpose of this invention to provide fatty acid compositionswhich may be employed in soap compositions'to achieve thebenefitsderived from coconut fatty It has been generally assumed that the highcontent of C12 lauric acid, in coconut and similar fats, has beenresponsible for properties of the soaps and that the other acids presentwere largely inert if not actually detrimental. We have found, however,that a very much smaller amount of lower chain length acids ranging fromCa to C10 in chain length will confer upon soapsthe propertiesordinarily obtainable only with considerable larger" amounts of coconutor similar 'oils containing a high percentage of lauric acid.

We have found, for example, that a composition consist-ing of 15% of C9pelargonic acid and commer' cial oleic acid will produce a liquid potashsoap of 36%" concentration and a viscosity of 82 centipoises. It isnecessary to use approximately 50% of coconut acids and 50% oleic acidto obtain an equivalent soapsolution,

Pelargonic acid is readily produced by the oxidation of oleic acidobtainable from a wide variety'of 'fatsarid is, therefore, not dependentupon the price of anysingle' The Cs, Ca, and C10 acids which areobtainable from the fractionation of coconut acids are also suitable rawfat.

for improving soap properties but are dependent upon the price andavailability of coconut and similar oils.

The C6 acid, caproic, can be manufactured synthetically or separatedfrom natural fats and is suitable for improving soap.

A mixture of from 10 to 15% of Ca toCio acids with to 85% of oleic acidor olive, oil acids provides bar soaps which do not show a surfacesliminess in use, which is characteristic of low titre bar soapscomposed primarily of unsaturated acids. From 40 to 50% of coconut oilmust be used to accomplish this same result. Likewise, 15 to 20% of lowmolecularweight acids may be blended with tallow acids to. prepare agranular laundry 'soap whose particle's will'not fuse together or ball.when poured into water. a

Whereasit has been widely assumed that the lower chain length acidspresent in coconut oil were'responsible for its:irritant properties, wehave found that soaps prepared from a mixture of representative lowmolecular weight "acids of the type previously described and the usualC1s'-.C1a acidsare actually less irritating than soaps having similarphysical properties prepared with coconut 'oil. The soaps. prepared withthe representative C or lower acids will contain a somewhat greateramount of the soaps of the C6 and Cm acids than the same soaps preparedwith coconut oil but will contain little or no soaps of the C12 and C14acids. Whether the irritation caused by coconut oil is due to thepresence of the soaps of C12 and C14 acids or to a greater totalpercentage of soaps of acids lower than C16 or to some other irritantpresent in the natural oil has not been determined but the fact remainsthat, surprisingly enough, blended soaps containing sufiicientrepresentative Cw'or lower acids to achieve desirable physicalpropertiesare less irritating than the high proportion of coconut oilwhich would be ordinarily required to produce equivalent results.

I The comparative irritant effect was determined by the Rabbits Eye Test(Draize, J. Pharmacol and Exp. Therap., vol. 82, No. 4,'December 1944)in which a few drops-of soap solutions of 10% concentration were placedin the eyes of test rabbits and the degree of redness, swelling, orother damage estimated by observation according to a preset scale ofvalues. By this test, the soaps containing representative low molecularweight acids consistently showed less irritation than soaps containingcoconut oil acids.

The soaps were also used and graded under code numbers by variousindividuals and the soaps containing representative low molecular weightacids were judged to be less irritating.

Ourinvention is more fully illustrated but is not' limited by thefollowing examples:

Example 1.--A 36% liquid potash soap is prepared by mixing 85 parts ofcommercial oleic acid, parts commercial pelargonic acid, 26.7 partssolid potassium hydroxide, and 193.3 parts water. The resulting soapsolution is clear and sparkling having a viscosity of 82 centipoises at70 F.

A 20% liquid potash soap is prepared by mixing 100 parts of commercialoleic acid, 23.7 parts of solid potassium hydroxide, and 444.3 partswater. The viscosity ofthe resulting soap solution is 280 centipoises at70 F.

Example 2.-A 36% liquid potash soap is prepared by mixing .85 parts ofcommercial oleic acid, 15 parts commercial pelargonic acid, 26.7 partssolid potassium hydroxide, and 193.3 parts water. The resulting soapsolution is clear and sparkling having a viscosity of 82 centipoises at70 F. The soap solution does not gel or sep arate when cooled to 35 F.and held at this temperature for 24 hours. 7

An equivalent liquid soap solution requires the use of 50 parts ofcoconut fattyacid and 50 parts of commercial oleic acid, 27.7 partspotassium hydroxide, and 195.3 parts water. The viscosity of this soapsolution is 89.5 centipoises. Storage properties are similar to thepreviously described soap of oleic and pelargonic acids.

Example 3.A 36% liquid potash soap is prepared having a viscosity of 48centipoises at 70 F, Thesoap solution does not gel or separate whencooled to 35 F. and held at this temperature for 24 hours.

Example 4.A 25% soap solution is prepared by mixing 90 parts commercialdistilled tall oil acids, 20 parts solid potassium hydroxide and 295parts water. The soap solution is slightly hazy exhibits a viscosity of125 centipoises'at 70 F.

A 33% soap solution is prepared by' mixing 81 parts commercial distilledtall oil, 9 parts commercial pelargonic acid, 22 parts potassiumhydroxide, and 202-parts water. The resulting soap solution is clear andsparkling having a viscosity of 65 centipoises at 70 'F. The soapsolution does not gel or se'parate when cooled to 35 F. and held at thistemperature for 24 hours.

Example 5.-Bar soaps suitable for hand and body washing are prepared bymixing (A) 98 parts commercial oleic acid, 2 parts adipic acid, 15.2parts solid sodium hydroxide, and 35.3 parts water, (B) 78 partscommer-' cial oleic acid, 20 parts commercial pelargonic acid, '2 partsadipic acid, 17.6 gms. sodium hydroxide, and 35.4 parts water, (C) 48parts commercial oleic acid, 50 parts coconut fatty acids, 2 partsadipic acid, 17.6 parts sodium hydroxide, and 35.4 parts water.

An objectionable slime develops on the surface of the bar soaprepresented by formula (A) when this bar is used for hand washing. Theobjectionable sliminess does not appear when bars represented byformulas (B) and (C) are used for hand washing under the sameconditions.

Bars represented by formulas (A), (B) and (C) are immersed in water for16 hours at 70 F. At the end of this period, the bar soap represented byformula (A) has approximately doubled in size and has'almostdisintegrated, becoming so'slimy and soft as to be entirely unsuitableas a bar soap. Under the same condition of immersion in water for 16hours at 70 F., the bar soaps represented by formulas (B) and (C) haveincreased'in size only approximately 1020%. After immersion in water,bar soaps (B) and (C) have softened to some extent but still retainsuitability as bar soaps.

Example 6.Soaps are prepared by mixing (A) 100 parts commercialdistilled tallow fatty acids, 14.6 parts sodium hydroxide, 10 partscommercial sodium silicate, and 43.4 parts water, (B) 85 partscommercial distilled tallow fatty acids, 15 parts commercial pelargonicacid, 16.5 parts sodium hydroxide, 10 parts sodium silicate and 44.5parts water, (C) parts commercial distilled talfrom parts commercialoleic acid and 15 parts caprylic v acid. The soap solution is preparedin the same manner as the soaps described in Example 2 with anappropriate adjustment in the quantity of'potassium hydroxide and water.The resulting soap solution is clear andxsparkling low fatty acids, 40parts commercial coconut fatty acids, 16.5 parts sodium hydroxide, 10parts sodium silicate,'and 44.5 parts water.

The soaps represented by formulas (A), (B) and (C) a are dried andconverted to powder andgranulated'soaps.

The conversion maybe accomplished by spraying molten soap through anozzle into a cylindrical vertical tower containing circulating hot airor passing the soap in a. flake form through a Procter-Schwartz drierwith subsequent grinding. to a powder. Whichever methods may be used,soaps (A), (B) and (C) are converted to powders or granules containingan appreciable proportion, say 10%, that will pass through a meshscreen. The comminuted soaps are then tested by pouring 10 to 50 gms. ofthe soap into a'dishpan of water at 100 'F. to F. and allowed to standfor five (5) minutes with no agitation or gentle agitation. After thistreatment the powdered soap represented by formula (A) has formed agummy, sticky paste that is diflicult to disperse even with considerableagitation. Under the same conditions, the powdered soaps represented byformulas (B) and (C) are easily dispersed in hot water.

In general, the liquid soaps of this invention are constituted by makingwater solutions of the potassium salts of mixed fatty acids, 75 to 95%of the fatty acids being predominantly aliphatic, monocarboxylic,unsaturated acids of 18 carbon chain length and 25 'to 5% aliphatic,

monocarboxylic, saturated acids of 6 to 10 carbons chain length. The barsoaps of this invention may utilize substantially the same ratios of thesame acids as the liquid soaps, but the bar soaps are preferablyconstituted by neutralizing the acids with sodium compounds to providesodium salts rather than potassium salts.

In general, the fatty acids utilized are not absolutely pure fattyacids, that is, commercial oleic acid conventionally contains bothstearic and palmitic acids in minor amounts and also polyunsaturatedacids such as linoleic acid in minor amounts. In general, the liquidacids are cheaper than the solid acids, but the separation need not becomplete. Any naturally occurring mixture of fatty acids may be used formanufacturing these soaps and the percentage of short chain length acidsadjusted to provide a soap of characteristics desired for any specificpurpose. Also, all of the recognized soap builders and additives may beincorporated in the soaps of this invention, the amount of short chainlength acids being adjusted to provide the desired characteristics forthe soap in question.

Having described my invention, I claim:

1. A bar soap comprising the sodium salts of 75 to 95% liquidunsaturated aliphatic monocarboxylic acids of 18 carbons chain lengthand the sodium salts of 25 to aliphatic monocarboxylic saturated acidsof from 6 to 10 carbons chain length.

2. A liquid soap comprising water and the potassium salts of fattyacids, 75 to 95 of said fatty acids being liquid unsaturated aliphaticmonocarboxylic acids of 18 carbons chain length and to 5% of said fattyacids being aliphatic monocarboxylic saturated fatty acids of from 6 to10 carbons chain length.

3. An admixture of aliphatic monocarboxylic acids adapted for themanufacture of sodium and potassium soaps consisting essentially of toacids of 16 to 18 carbon atoms chain length and 25-5% acids of 6 to 10carbon atoms chain length.

4. An admixture set forth in claim 3 wherein said acid of 16 to 18carbon atoms chain length is commercial oleic acid and said acid of 6-10carbon atoms chain length is commercial pelargonic acid.

Chemical Formulary, Bennett, Van Nostrand C0. New York, vol. 3 (1936),page 323.

1. A BAR SOAP COMPRISING THE SODIUM SALTS OF 75 TO 95% LIQUIDUNSATURATED ALIPHATIC MONOCARBOXYLIC ACIDS OF 18 CARBONS CHAIN LENGTHAND THE SODIUM SALTS OF 25 TO 5% ALIPHARIC MONOCARBOXYLIC SATURATEDACIDS OF FROM 6 TO 10 CARBONS CHAIN LENGTH.